Water softeners find wide applications throughout society. In many applications, it is desirable to soften the water by removing the hardness minerals from the water before use. This is particularly critical in boiler operation where use of hard water will create boiler scale and rapidly reduce operating efficiencies.
A common water softening process is to use water softeners designed for this purpose. Water softening tanks contain cation exchange resin capable of exchanging hardness ions, i.e., calcium and magnesium for sodium ions which are very soluble.
When the hardness exchanging capacity of the water softening resin has exhausted it stops producing soft water. It then becomes necessary to regenerate the resin with a saturated solution of sodium or potassium chloride. Because of cost, sodium chloride is usually the chemical of choice.
Sodium chloride brine solution is made in a separate tank built and designed for this purpose, and this tank is called a brine tank.
Modern water softeners are well engineered and designed to produce soft water with all regeneration actions done automatically, including the transfer of the saturated brine from the brine tank to the water softener tanks.
In order for the water softener resin to be properly rejuvenated, the saturated brine solution must be of high quality and a measured volume must be delivered whenever needed.
A properly designed and engineered brine tank will provide these needs by delivering a measured quantity of saturated salt brine containing a fixed amount of dissolved salt per gallon of water.
This is accomplished by using a horizontal salt grid in a vertical tank. The height and diameter of the salt grid varies for each softening system, depending on many factors, but in all cases the height of the salt grid sets the volume of water in the brine tank.
In actual practice, the brine system is set to fill the brine tank with fresh water from the bottom of the tank to approximately 1" above the salt grid and then shut off.
Using this method, only 1" of water touches the vertical salt pile, which may be several hundred pounds in weight, stored on top of the salt grid.
This system is called a dry salt shelf system, as opposed to a wet salt brine tank system where most or all the salt is immersed in water. The dry salt shelf system has significant advantages over the wet salt system. The dry salt shelf method produces 100% saturated brine (specific gravity 1.2) all the time where wet salt methods do not. The dry salt shelf system affects more dry salt storage in the same size brine tank than a wet salt system. A dry salt shelf system is easier to keep clean than the wet salt system. A dry salt shelf system does not require a gravel support bed at the bottom of the brine tank. The dry salt shelf system offers lower maintenance costs to the operator, no gravel cleaning or replacement.
The dry salt shelf system has no messy brine float valves as used above the liquid brine on wet salt systems. These float valves become corroded with salt creep and require repair and/or replacement frequently. The dry salt shelf system uses brine float or refill valves in the lower section of the brine tank (below the shelf) and are less exposed to the risk of malfunctions or corrosion, thus operating more efficiently. The dry salt shelf system uses all of the salt stored before the brine tank needs to be refilled. Liquid below the shelf is saturated brine even if only one grain of salt remains on the shelf. The brine tank salt refill is less often with the dry salt shelf system because of the greater salt storage capacity it offers. Brine tank corrosion is reduced or eliminated on steel brine tanks with the dry salt shelf system because the liquid level is down below the dry salt, thus less air/brine exposure. The dry salt shelf system allows more programmed salt delivery scheduling because the salt stored is easily seen and thus the quantity remaining can be easily determined. The dry salt shelf system allows the use of all grades of salt, even the most economical rock type salt. The dry salt shelf type brine system can be cleaned in less than one hour, regardless of size whereas a wet salt tank may take one day and require the water softener to be down.
Dissolving of salt starts immediately and continues until the volume of water beneath the salt grid becomes saturated with dissolved salt. When saturation occurs, dissolving ceases. Stored salt above the salt grid not in contact with the water remains dry, preventing bridging and mushing.
Using a salt grid enables an engineer to calculate the quantity and quality of a particular size brine tank will produce. The engineer then is able to select the proper brine tank for the water softener system. It is imperative that the grid and support system be strong to support the mass of weight placed upon it. Until now, salt grids and support systems have usually been made from pegboard. It is readily available and cheap; however, in contact with the salt brine it tends to deform, warp and those portions of the salt grid left unsupported tend to break and collapse, dumping the salt stored on them down into the brine measuring area.
When this occurs, it causes the water softener to malfunction.
The salt grid and support system must be rebuilt, and in time it fails again.
For these reasons, the salt grid and support system could not be used in larger brine tanks.
As the demand increased for larger and larger water softeners, the demand for more saturated brine increased.
In order to provide this requirement, brine tanks increased in size and the pegboard salt grid and support system could not be used as they were not strong enough to hold the weight.
These larger systems were forced to use the less efficient older method of wet storage.
This method consists of loading the brine tank with several hundred pounds of gravel on the bottom. Several hundred pounds of salt is then poured upon the gravel and water is then added until a portion or all of the salt is submerged.
The measuring advantage of the salt grid system is lost.
The salt brine produced by the wet salt storage method is often of poor quality and submerged salt tends to bridge and mush, causing maintenance problems.
The salt grid plate and support system we have designed and built is strong enough that it may be used in the larger systems.
Again, the engineer can calculate the exact quantity of brine needed by utilizing the salt grid method.